Variable valve lift apparatus

ABSTRACT

A variable valve lift apparatus of an engine may include an inner tappet, an outer tappet centrally receiving the inner tappet, a latching unit inserted in the inner tappet and operated by a hydraulic pressure so as to selectively engage the inner and outer tappets by operation, and a protruding member that is coupled to an upper surface edge of the outer tappet so as to protrude outward from an exterior circumference of the outer tappet, and is vertically slidable along a sliding groove of a cylinder head.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2010-0089961 filed Sep. 14, 2010, the entire contents of which application is incorporated herein for all purposes by this reference.

BACKGROUND OF INVENTION

1. Field of Invention

The present invention relates to a variable valve lift apparatus. More particularly, the present disclosure relates to a variable valve lift apparatus preventing rotation of a variable tappet installed therein.

2. Description of Related Art

An internal combustion engine produces power by taking in fuel and air and burning them in a combustion chamber.

While an intake valve is open by an operation of a camshaft, air is drawn into the combustion chamber. While an exhaust valve is open by the operation of the camshaft, combustion gas is exhausted from the combustion chamber.

An optimal operation of intake and exhaust valves depends on a rotation speed of an engine. That is, an optimal lift and/or opening/closing timing of the valves depend on the engine speed.

In order to achieve the optimal valve operation depending on the engine speed, a variable valve lift (VVL) apparatus, which varies the lifts of the valves depending on the engine speed, has been proposed.

In a conventional scheme of a variable valve lift apparatus, high and low cams and corresponding inner and outer tappets are employed so that high and low cams contact and operate corresponding inner or outer tappets, respectively. In such a scheme, rotation of tappets around their axis of cylindrical shape should be prevented, because otherwise it may happen that cams may fail to operate corresponding tappets and an engine damage may be caused.

The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

SUMMARY OF INVENTION

Various aspects of the present invention provide for variable valve lift apparatus of an engine having advantages of preventing rotation of valve tappets.

One aspect of the present invention is directed to a variable valve lift apparatus of an engine includes an inner tappet, an outer tappet centrally receiving the inner tappet, a latching unit inserted in the inner tappet and operated by a hydraulic pressure so as to selectively engage the inner and outer tappets by operation, and a protruding member that is coupled to an upper surface edge of the outer tappet so as to protrude outward from an exterior circumference of the outer tappet, and is vertically slidable along a sliding groove of a cylinder head.

A supporting recess having a predetermined width may be formed across a center of the uppermost portion of the outer tappet.

An exterior diameter of the uppermost portion of the inner tappet may be smaller than or equal to an exterior diameter of the outer tappet.

A cross-section of the inner tappet may be generally T-shaped.

The protruding member may include a first portion coupled with an edge of the supporting recess, and a second portion perpendicularly connected to the first portion and protruding outward from the exterior circumference of the outer tappet.

A cross-section of the protruding member may be generally L-shaped.

A mounting groove may be formed at the edge of the supporting recess so as to allow coupling of the first portion.

A bottom surface of the first portion may coincide with a bottom surface of the supporting groove.

An exterior of the second portion protruding from the exterior circumference of the outer tappet may be round.

An exterior of the second portion protruding from the exterior circumference of the outer tappet may be polygonal.

The protruding member may be fixed to the outer tappet by pressing, welding, bonding, bolting, or fusion.

Another aspect of the present invention is directed to a variable valve lift apparatus in which a rotation of tappet by repeated contact with cams may be prevented since the protruding member engaged to the upper surface edge of the outer tappet is inserted in the sliding groove of the cylinder head.

Therefore, according to various embodiments, the high cam and the low cam may respectively stay on the outer tappet and the inner tappet, and lubricant supply may be stable by precisely maintaining the connection of supply oil supply passages in the outer tappet and the cylinder head.

In addition, the protruding member is installed at the uppermost edge portion of the outer tappet that is thicker than the skirt portion, and thus the degree of freedom in designing an area of installing the protruding member at the outer tappet may become larger.

Furthermore, such a feature provides that strength, durability, and structural stability of an entire apparatus may be improved since the protruding member may be held sufficiently and firmly.

According to various embodiments, the protruding member may be immediately installed to the uppermost portion edge of the outer tappet by a very simple operation without requiring an additional fabricating or modifying process such as drilling a hole into the outer tappet.

In addition, according to various embodiments, a large degree of freedom is provided in the shape and structure of the protruding member, and thus such a structure may be implemented into a various type of variable valve lift apparatus.

According to various embodiments, the cross-section of the inner tappet is generally T-shaped, and the supporting recess supporting the uppermost portion of the inner tappet is formed at the uppermost portion of the outer tappet. Therefore, an operable contact range of the inner tappet may be enlarged, and thereby the low lift running range may also be enlarged.

The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a high lift mode of a basic operation principle of an exemplary variable valve lift apparatus according to the present invention.

FIG. 2 shows a low lift mode of a basic operation principle of an exemplary variable valve lift apparatus according to the present invention.

FIG. 3 is a perspective view showing an exemplary variable valve lift apparatus according to the present invention.

FIG. 4 is an exploded perspective view of FIG. 3.

FIG. 5 is a plan view of FIG. 3.

FIG. 6 is a cross-sectional view of FIG. 3 according to line A-A.

FIG. 7 is a cross-sectional view of FIG. 3 according to line B-B.

FIG. 8 illustrates an assembly of a cylinder head installed with an exemplary variable valve lift apparatus according to the present invention.

FIG. 9 illustrates an exemplary variation of a protruding member that may be used in a variable valve lift apparatus according to the present invention.

FIG. 10 is a perspective view of another exemplary variable valve lift apparatus according to the present invention.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.

Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification.

The size and thickness of each element are arbitrarily shown in the drawings, and the present invention is not necessarily limited thereto, and in the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity.

Hereinafter, the principal operation of a variable valve lift apparatus according to various embodiments of the present invention is described with reference to FIG. 1 and FIG. 2.

FIG. 1 and FIG. 2 respectively show a high lift mode and a low lift mode of a basic operation principle of a variable valve lift apparatus according to various embodiments of the present invention.

In the high lift mode, an hydraulic pressure is supplied to a hydraulic pressure chamber 240 formed in an outer tappet 30 and a latching pin 31 is pushed by the supplied hydraulic pressure. Then, as shown in FIG. 1, while a latching pin support pin 53 is fixedly inserted in the inner tappet 10, inner and outer tappets 10 and 30 are engaged because the latching pin 31 is inserted into a latching pin receiving recess 340 by compressing a return spring 55.

Here, high cams 212 formed at a camshaft 210 press the outer tappet 30 upon a rotation of the camshaft 210, and the inner and outer tappets 10 and 30 integrally reciprocates vertically. By such an operation, a high lift mode is achieved.

In the low lift mode, as shown in FIG. 2, the hydraulic pressure is released from the hydraulic pressure chamber 240. Then, while the latching pin support pin 53 is fixedly inserted in the inner tappet 10, the latching pin 31 is separated from the latching pin receiving recess 340 by a restoring force of the return spring 55. Therefore, in this case, the inner and outer tappets 10 and 30 are separated and move independently.

In this case, a valve is opened or closed by the inner tappet 10 that reciprocates by a rotation of the low cam 214 formed at the camshaft 210, and the outer tappet 30 merely reciprocates by a lost motion spring without affecting the valve operation.

FIG. 3 is a perspective view showing a variable valve lift apparatus according to various embodiments of the present invention. FIG. 4 is an exploded perspective view of FIG. 3. FIG. 5 is a plan view of FIG. 3. FIG. 6 is a cross-sectional view of FIG. 3 according to line A-A. FIG. 7 is a cross-sectional view of FIG. 3 according to line B-B.

Referring to the drawings, a variable valve lift apparatus 100 according to various embodiments of the present invention devised to enlarge a low lift operating range and to prevent a variable tappet from rotating with respect to a cylinder head while maintaining durability.

For such a purpose, a variable valve lift apparatus 100 according to various embodiments of the present invention includes an inner tappet 10, an outer tappet 30, a latching unit 50, and a protruding member 80.

The inner tappet 10 includes a body portion 11 of a cylindrical shape, and a head portion 13 integrally formed to a top of the body portion 11.

The head portion 13 having a predetermined width and length is fixedly formed at the top of the body portion 11. At a connection portion of the head portion 13, a first insert hole 15 is formed such that a latching unit 50 may be inserted therethrough along a width direction of the head portion 13.

The body portion 11 is connected to the head portion 13, vertically with respect to a horizontal direction of the head portion 13, such that a vertical cross-section becomes a T shape.

By forming the inner tappet 10 in the generally T shape, wider range of valve timing may be allowed for a low lift mode of an engine by allowing a low cam 214 (refer to FIG. 1) to contact the inner tappet 10 at a wide range.

In addition, by forming the inner tappet 10 in the generally T shape, a space for mounting the protruding member 80 to the outer tappet 30 may be securely formed.

A tappet coupling portion 31 is formed at a center of the outer tappet 30 such that the body portion 11 of the inner tappet 10 may be inserted thereinto. A skirt portion 33 extending downward from uppermost portion of the outer tappet 30 is formed at exterior circumference of the outer tappet 30.

A second insert hole 35 is formed at the uppermost portion of the outer tappet 30. The second insert hole 35 is connected with the first insert hole of the inner tappet 10, and the latching unit 50 inserted in the first insert hole 15 is also partially inserted into the second insert hole 35.

Considering such an arrangement, the uppermost portion of the outer tappet 30 may be formed thicker than the skirt portion 33.

A supporting recess 37 is formed at the uppermost portion of the outer tappet 30 so as to support the head portion 13 of the inner tappet 10.

The supporting recess 37 having a predetermined width is formed across a center of the tappet coupling portion 31, and is of a generally rectangular shape such that longer and parallel sides of the head portion 13 may contact the recess and slide upward.

Edges of the head portion 13 of the inner tappet 10 except the longer and parallel sides are formed in a generally round shape, of which an exterior diameter may be formed smaller than an exterior diameter of the outer tappet 30 such that the protruding member 80 may be installed at the supporting recess 37.

The latching unit 50 is employed to selectively engage the inner tappet 10 with the outer tappet 30 by an hydraulic pressure.

The latching unit 50 includes a latching pin 51 that is inserted in the first insert hole 15 of the inner tappet 10 and also partially inserted in the second insert hole 35 of the outer tappet 30.

The latching pin 51 is generally cylindrical shape in which a hollow space is formed, and a support pin 53 penetrates the latching pin 51. A return spring is installed inside the latching pin 51.

In the present exemplary embodiment, the protruding member 80 provides a function of preventing rotation of the inner and outer tappets 10 and 30 with respect to the cylinder head 90 (refer to FIG. 8).

The protruding member 80 is mounted to the uppermost portion of the outer tappet 30 and protrudes outward from the exterior circumference of the outer tappet 30, such that the protruding member may slide vertically along a sliding groove 91 (refer to FIG. 8) of the cylinder head 90.

In more detail, the protruding member 80 is installed at an edge of the supporting recess 37, and a mounting groove 39 is formed at the edge of the supporting recess 37 so that the protruding member 80 may be installed thereto.

The protruding member 80 includes a first portion 81 and a second portion 82. The protruding member 80 is mounted to the mounting groove 39 by the first portion 81. The second portion is formed perpendicular to the first portion 81 and protrudes outward from the exterior circumference of the outer tappet 30.

That is, a cross-section of the protruding member 80 is generally L shaped. A bottom surface of the first portion 81 coincides with a bottom surface of the supporting groove 37. An exterior of the second portion 82 protruding from the exterior circumference of the outer tappet 30 is formed round.

The first portion 81 of the protruding member 80 may be fixed to the mounting groove 39 by various ways such as pressing, welding, bonding, bolting, and fusion.

A reference numeral 98 indicates a lost motion spring and a reference numeral 99 indicates a valve.

By such an arrangement of a variable valve lift apparatus 100 according to various embodiments of the present invention, as shown in FIG. 8, the second portion 82 of the protruding member 80 can merely slide vertically along the sliding grove 91, and a rotation is prevented by the second portion 82.

In various embodiments, an exterior of the second portion 82 protruding from the exterior circumference of the outer tappet 30 may be formed round. However, as shown in FIG. 9, an exterior of the second portion 82 protruding from the exterior circumference of the outer tappet may be formed polygonal.

As described above, according to a variable valve lift apparatus according to various embodiments of the present invention 100, rotation of tappet due to contacting a cam may be prevented since the protruding member 80 engaged to the upper surface edge of the outer tappet 30 is inserted in the sliding groove 91 of the cylinder head 90.

Therefore, according to various embodiments, the high cam 212 (refer to FIG. 1) and the low cam 214 (refer to FIG. 1) may respectively stay on the outer tappet 30 and the inner tappet 10, and lubricant supply may be stable by precisely maintaining the connection of supply oil supply passages in the outer tappet 30 and the cylinder head.

In addition, the protruding member 80 is installed at the uppermost edge portion of the outer tappet 30 that is thicker than the skirt portion 33, and thus the degree of freedom in designing an area of installing the protruding member 80 at the outer tappet 30 may become larger.

Furthermore, such a feature provides that strength, durability, and structural stability of an entire apparatus may be improved since the protruding member 80 may be held sufficiently and firmly.

According to various embodiments, the protruding member 80 may be immediately installed to the uppermost portion edge of the outer tappet 30 by a very simple operation without requiring an additional fabricating or modifying process such as drilling a hole into the outer tappet 30.

In addition, according to various embodiments, a large degree of freedom is provided in the shape and structure of the protruding member 80, and thus such a structure may be implemented into a various type of variable valve lift apparatus.

According to various embodiments, the cross-section of the inner tappet 10 is generally T-shaped, and the supporting recess 37 supporting the uppermost portion of the inner tappet 10 is formed at the uppermost portion of the outer tappet 30. Therefore, an operable contact range of the inner tappet 10 may be enlarged, and thereby the low lift running range may also be enlarged.

FIG. 10 is a perspective view of a variable valve lift apparatus according to another exemplary embodiment of the present invention.

Referring to the drawing, a variable valve lift apparatus according to other embodiments of the present invention 400 is similar to and based on the above-described described embodiments. Major difference in the two embodiments is that an exterior diameter of the head portion 113 of the inner tappet 110 is equal to an exterior diameter of the outer tappet 130.

That is, the head portion 113 of the inner tappet 110 that couples with the supporting recess 137 of the outer tappet 130 is of a same length with the supporting recess 137.

In various embodiments, the lower surface of the head portion 113 of the inner tappet 110 may help securing the first portion 181 to the mounting groove 39 while being coupled to the supporting recess 137 of the outer tappet 130.

Therefore, according to various embodiments where the exterior diameter of the head portion 113 of the inner tappet 110 is the same with the exterior diameter of the outer tappet 130, strength and durability of the protruding member 180 with respect to the outer tappet 130 may be further improved since the protruding member 180 may be held more firmly.

Other features of the variable valve lift apparatus 400 according to various embodiments of the present invention is the same as, similar to, or apparent from the disclosure regarding the first exemplary embodiment, and further detailed description thereto has been shortened.

For convenience in explanation and accurate definition in the appended claims, the terms upper or lower, inside or outside, and etc. are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures.

The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents. 

What is claimed is:
 1. A variable valve lift apparatus of an engine, comprising: an inner tappet; an outer tappet centrally receiving the inner tappet; a latching unit within the inner tappet and operated by a hydraulic pressure so as to selectively interengage the inner and outer tappets; and a protruding member that is coupled to an upper surface edge of the outer tappet protruding outward from an exterior circumference of the outer tappet, and is vertically slidable along a sliding groove of a cylinder head.
 2. The variable valve lift apparatus of claim 1, wherein a supporting recess having a predetermined width is formed across a center of an uppermost portion of the outer tappet.
 3. The variable valve lift apparatus of claim 2, wherein an exterior diameter of the uppermost portion of the inner tappet is smaller than or equal to an exterior diameter of the outer tappet.
 4. The variable valve lift apparatus of claim 3, wherein a cross-section of the inner tappet is generally T-shaped.
 5. The variable valve lift apparatus of claim 3, wherein the protruding member comprises: a first portion coupled with an edge of the supporting recess; and a second portion perpendicularly connected to the first portion and protruding outward from the exterior circumference of the outer tappet.
 6. The variable valve lift apparatus of claim 5, wherein a cross-section of the protruding member is generally L-shaped.
 7. The variable valve lift apparatus of claim 5, wherein a mounting groove is formed at the edge of the supporting recess so as to allow coupling of the first portion.
 8. The variable valve lift apparatus of claim 7, wherein a bottom surface of the first portion coincides with a bottom surface of the supporting groove.
 9. The variable valve lift apparatus of claim 5, wherein an exterior of the second portion protruding from the exterior circumference of the outer tappet is round.
 10. The variable valve lift apparatus of claim 5, wherein an exterior of the second portion protruding from the exterior circumference of the outer tappet is polygonal.
 11. The variable valve lift apparatus of claim 1, wherein the protruding member is fixed to the outer tappet by pressing, welding, bonding, bolting, or fusion. 